Math Problem Statement

please expand 1/2 \times \ln (e^{2x} - 2x) as a taylor series in x

Solution

We can expand 12ln(e2x2x)\frac{1}{2} \ln(e^{2x} - 2x) into a Taylor series around x=0x = 0. Let’s break this process into steps:

Step 1: Write the expression.

We are expanding: f(x)=12ln(e2x2x)f(x) = \frac{1}{2} \ln(e^{2x} - 2x)

Step 2: Expand e2xe^{2x} as a Taylor series.

The Taylor series expansion of e2xe^{2x} around x=0x = 0 is: e2x=1+2x+2x2+4x33+4x43+e^{2x} = 1 + 2x + 2x^2 + \frac{4x^3}{3} + \frac{4x^4}{3} + \dots

Step 3: Substitute into e2x2xe^{2x} - 2x.

Substitute the series into e2x2xe^{2x} - 2x: e2x2x=(1+2x+2x2+4x33+)2x=1+2x2+4x33+e^{2x} - 2x = \left(1 + 2x + 2x^2 + \frac{4x^3}{3} + \dots \right) - 2x = 1 + 2x^2 + \frac{4x^3}{3} + \dots

Step 4: Take the natural logarithm.

To expand ln(1+u)\ln(1 + u), use the series: ln(1+u)=uu22+u33\ln(1 + u) = u - \frac{u^2}{2} + \frac{u^3}{3} - \dots Here, u=2x2+4x33+u = 2x^2 + \frac{4x^3}{3} + \dots. Substituting:

= 2x^2 + \frac{4x^3}{3} - \frac{1}{2}(2x^2)^2 + \dots$$ ### Step 5: Simplify terms. Expand and collect terms up to desired order: $$\ln(e^{2x} - 2x) = 2x^2 + \frac{4x^3}{3} - 2x^4 + \dots$$ ### Step 6: Multiply by $$\frac{1}{2}$$. Finally, multiply by $$\frac{1}{2}$$: $$f(x) = \frac{1}{2} \ln(e^{2x} - 2x) = x^2 + \frac{2x^3}{3} - x^4 + \dots$$ ### Final Taylor Series: $$\frac{1}{2} \ln(e^{2x} - 2x) = x^2 + \frac{2x^3}{3} - x^4 + \dots$$ Let me know if you'd like more detailed steps or higher-order terms! --- ### Questions to explore: 1. How do we generalize the logarithmic expansion for more complex functions? 2. Why do Taylor series converge near $$x = 0$$ for analytic functions? 3. How does the $$e^{2x}$$ term dominate the expansion for large $$x$$? 4. What would the Taylor series of $$\ln(e^{2x} + 2x)$$ look like? 5. Can you visualize the approximation using a graph? ### Tip: Always check the radius of convergence for Taylor series to ensure the approximation is valid in your region of interest.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Taylor Series
Logarithmic Expansion
Exponential Functions

Formulas

Taylor Series Expansion for e^x: e^x = 1 + x + x^2/2! + x^3/3! + ...
Logarithmic Series Expansion: ln(1 + u) = u - u^2/2 + u^3/3 - ...
Taylor Series for ln(e^x - 2x)

Theorems

Taylor's Theorem
Logarithmic Expansion
Exponential Series Expansion

Suitable Grade Level

Grades 11-12